Lectrosonics UM200c User Manual

UM200C

FREQUENCY-AGILE UHF

BELT-PACK TRANSMITTER

OPERATING INSTRUCTIONS

LECTROSONICS, INC.

Rio Rancho, NM

www.lectrosonics.com

UM200C

TABLE OF CONTENTS

INTRODUCTION .................................................................................................. 3

GENERAL TECHNICAL DESCRIPTION ............................................................ 4

CONTROLS AND FUNCTIONS .......................................................................... 6

BATTERY INSTALLATION ................................................................................... 8

OPERATING INSTRUCTIONS ............................................................................ 8

OPERATING NOTES ........................................................................................... 9

ADJUSTING THE TRANSMITTER FREQUENCY.............................................. 9

MICROPHONE CORD TERMINATION ............................................................. 10

5-PIN INPUT JACK WIRING.............................................................................. 11

TROUBLESHOOTING......................................................................................... 14

SPECIFICATIONS AND FEATURES ................................................................. 15

SERVICE AND REPAIR ...................................................................................... 16

RETURNING UNITS FOR REPAIR .................................................................... 16

WARRANTY ..........................................................................................Back cover

The UM200C transmitter is FCC type accepted under Part 74: 470-608MHz and 614-802MHz

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LECTROSONICS, INC.

Frequency Agile UHF Belt-Pack Transmitter

INTRODUCTION

Thank you for selecting the Lectrosonics UM200C frequency agile, belt-pack trans­mitter. The UM200C combines over 80 years of engineering experience with the very
latest components, in a design that addresses the most demanding professional
applications.

The design of the UM200C was the direct result of numerous conversations with
users, staging and touring companies and dealers across the US. The specific
concerns and needs brought up in these conversations led directly to the develop­ment of the operational features offered on the UM200C. Two hundred fifty six
frequencies are user selectable in 100kHz steps to alleviate interference problems in
travelling venues, and the low frequency roll-off is user adjustable to adapt to varying
acoustic environments and preferences.

The UM200C is a rugged, machined aluminum package with a removable, spring
loaded belt clip. The input section provides a correct input tap for virtually any
microphone or line level audio source. 5 Volts of bias voltage is available to power
electret mics with either positive or negative bias. Level indicating LEDs are provided
on the control panel to make level settings quick and accurate, without having to
view the receiver. The battery compartment accepts any 9 Volt alkaline battery and
makes a positive connection via self-adjusting contacts. The antenna is a detach­able, locking 1/4 wavelength flexible bronze cable that connects to a 50 Ohm SMA
port on the transmitter.

Only the UM200C transmitter is covered in this manual. Companion receivers are
covered in separate manuals. The UM200C will operate with any 200 Series Lec­trosonics receiver in the same frequency group.

Rio Rancho, NM – USA

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UM200C

GENERAL TECHNICAL DESCRIPTION

The UM200C transmitters are comprised of a number of functional sub-systems as shown in the block diagram below.

GENERAL

The 200 system uses 75kHz wide deviation for an extremely high signal to noise ratio.The transmitter circuits are all
regulated to allow full output power from the beginning (9 Volts) to the end (6.5 Volts) of battery life. The input ampli­fier uses a Motorola 33078 op amp for ultra low noise operation. It is gain controlled with a wide range input compres­sor which cleanly limits input signal peaks over 30dB above full modulation.

DUAL BAND COMPANDOR

Traditionally, compandors have been a source of distortion in wireless microphone systems. The basic problem with
conventional systems is that the attack and decay times are always a compromise. If the time constants are fast, high
frequency transients will not be distorted, but this will cause low frequency distortion. If the time constants are slower,
low frequency audio distortion will be low, but high frequency transients will then be distorted. The 200 system
introduces an entirely new approach to solving this basic problem, called “dual-band companding.”

There are actually two separate compandors in the 200 system, one for high frequencies and one for low frequencies.
A crossover network separates the frequency bands at 1kHz with a 6dB per octave slope, followed by separate high
and low frequency compandors. The attack and release times in the high frequency compandor are fast enough to
keep high frequency transient distortion at a low level, and the low frequency compandor uses slower time constants,
reducing low frequency distortion to well below that of a conventional compandor.

+5V BIAS

LIMIT

LED

SUPPLY

BUFFER

SHUNT

LIMITER

MIC

JACK

1
2
3
4
5

PHASE LOCKED LOOP

FREQ

SWITCHES

LP

FILTER

Vref

BASS

TREBLE

COMPANDED

<--See 5-Pin Input Jack Wiring for details.

LF
ROLL-OFF

INPUT
AMP

AUDIO
LEVEL

SET
LED

PEAK AUDIO

INDICATOR &

LIMITER
DRIVER

PRESCALER

DIVIDER

LOW PASS

FILTER

UM200C Block Diagram

COMPANDOR

LP FILTER

HP FILTER

AUDIO

PILOT
TONE

Vreg

Vreg

+3.6VDC

VOLTAGE

CONTROLLED

OSCILLATOR

OSC

+5VDC

TRANSMITTER

COMPANDED AUDIO

TO XMTR

PWR

DELAY

50

CIRCULATOR
ISOLATOR

+9VDC

PWR

LED

4

LECTROSONICS, INC.

Frequency Agile UHF Belt-Pack Transmitter

NO PRE-EMPHASIS/DE-EMPHASIS

The signal to noise ratio of the 200 system is high enough to preclude the need for conventional pre-emphasis (HF
boost) in the transmitter and de-emphasis (HF roll off) in the receiver. Pre-emphasis and de-emphasis in an FM radio
system usually provides about a 10dB improvement in the signal to noise ratio of the system, but the high frequency
boost in the transmitter must be removed in a purely complementary manner or else the frequency response of the
original audio signal will be altered.

Pre-emphasis can also cause distortion in the receiver. As this signal is passed through the IF filters in the receiver,
distortion can be produced, most noticeable at full modulation. De-emphasis cannot be applied until the signal is
converted into audio, so there is no way around this problem short of eliminating pre-emphasis altogether. Neither of
these problems occur in the 200 system. The dual-band compandor in the 200 Series system essentially provides a
dynamic pre-emphasis/de-emphasis function with extremely low distortion.

PILOT TONE SQUELCH

The 200 system utilizes an ultrasonic tone modulation of the carrier to operate the receiver squelch. This “pilot tone”
consists of a 32kHz signal mixed with the audio signal following the microphone preamp, just after the compandor, to
control the audio output muting of the receiver. The pilot tone is filtered out of the audio signal immediately after the
detector in the receiver so that it does not influence the compandor or various gain stages. The basic benefit of the
pilot tone squelch system is that the receiver will remain muted until it receives the pilot tone from the matching
transmitter, even if a strong RF signal is present on the carrier frequency of the system. This is extremely important in
applications that include an automatic microphone mixer.

WIDE-BAND DEVIATION

±75kHz deviation improves the capture ratio, signal to noise ratio and AM rejection of a wireless system dramatically,
compared to the more commonly used ±15kHz deviation.

LONG BATTERY LIFE

High efficiency circuits throughout the design allow over 4.5 hours of operation using a single 9 Volt alkaline battery.
(A 9V lithium battery will provide over 14 hours of operation.) The battery compartment is a unique mechanical
design which automatically adjusts to fit any brand of battery. The battery contacts are spring loaded to prevent
“rattle” as the unit is handled.

FREQUENCY AGILITY

The transmitter section uses a synthesized, frequency selectable main oscillator The frequency is extremely stable
over a wide temperature range and over time.

Two rotary switches, located on the side panel of the unit, provide 256 frequencies in 100kHz steps over a 25.5MHz
range. This alleviates carrier interference problems in mobile or travelling applications.

ANTENNA

At UHF frequencies, where wavelengths and antennas are shorter than at VHF frequencies, a resonant length wire is
preferred over using the microphone cable as the antenna. The antenna on the UM200C consists of a flexible 1/4
wavelength bronze cable, detachable via an SMA connector. The impedance of this connector is 50 Ohms.

Rio Rancho, NM – USA

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